Electrode for luminous positive column gaseous conducting devices



April 3, 1934. R. E. MIESSE 1,953,625

ELECTRODE FOR LUMINOUS POSITIVE COLUMN GASEOUS CONDUCTING DEVICES Filed April 4, 1930 frwenr' ffztarcZE/Vz'eaae Patented Apr. 3, 1934 ELECTRODE FOR LUMINOUS POSITIVE COLUMN GASEOUS CONDUCTING DE- VICES Richard E. Miesse, Chicago, Ill., assignor, by mesne assignments, to General Scientific Cor- Y poration, Chicago, 111., a corporation Application April 4, 1930,, Serial No. 441,530

4 Claims. (Cl. 176-l26) My invention relates to electrodes for positive column gaseous conduction tubes such as are used for illuminating signs and has as its principal object the provision of an electrode of this type which although it may be made very small in comparison with the current density used does not splutter sufficiently under the electrical discharge 'to delete the gas within the tube except after a very long period of time as the life of such tubes is measured.

More specifically it is a purpose of this invention to provide a tube of this character with electrodes having an interior coating of material capable of producing a relatively low cathode fall of potential and an exterior coating which is substantially incapable of transmitting electrical energy between the gas and the electrode body.

My invention also contemplates the provision in a tube of this character of a novel coating I for the electrode exterior by which substantial insulation of said exterior is obtained.

' More specifically my invention contemplates also the provision of coatings for the electrode which are particularly free of deleterious substances that would affect the color of the tube when excited.

Furthermore-my invention contemplates the provision of a novel composition for coating the interior of electrodes whereby to obtain a good emission surface therein.

I will describe one form which my invention may take by reference to the accompanying drawing wherein- Fig. 1 is a longitudinal view of a tube equipped with electrodes embodying my invention; and

' Fig. 2 is a longitudinal section through one of the electrodes shown in-Fig. 1.

Referring now in detail to the drawing, the numeral 5 indicates the usual glass tube .such as is used for display signs, this tube having a 'iilling of one or more of the. monatomic gases to give the tube the desired color. The exciting energy which causes the tube to glow is transmitted to the electrodes 6 and 7 from a suitable source of current through the lead-in wires 8 and 9 in a well known manner. I

The electrodes 6 and '1 are constructed as is shown in Fig. 2; that is, they consist of a tubular cylindrical portion 10 preferably made in the following manner: A cylinder of some suitable metal preferably nickel of approximately 9 mm. in length and 5 mm. in diameter, the pro- Jecting shoulder 11 2 mm.long and 2 mm. in diameter is'drilled to take the lead-in wire 8 upon which it is pressed rigidly.- The inside of the cylinder is then drilled from the end opposite the shoulder 11 with a hole 3 mm. in diameter and 8 mm. deep leaving a wall throughout the electrode proper of substantially 1 mm. in thickness.

.This electrode is then coated in a manner which ing a temperature of about 1200 degrees 0., for

a period of fifteen minutes. The electrodes on being degasified as above are assembled on the lead-in stems. The electrodes are-then heated in an oxygen flame to about 1250 degrees C., and thereafter the interior of the electrodes are coated with the inside coating.

This interior coating is preferably made up of a combination of a barium oxide having the formula BaOI-IzO and carbon which mixture is held in suspension by means of alcohol or acetone although it is kept quite thick in body. The percentage of carbon to barium compound is preferably made by weight between 1% and 15%, and the best results are obtained when 5% to 8% carbon is used. Nickel oxide may also be added as a binder although it is not necessary, and, in fact, the results obtained a e considerably better if no nickel oxide is use I have also found that instead of barium other alkaline earth metals such as calcium and strontium may be used for my purpose although the barium has proven.

more successful.

When the interior coating composition is made up in this manner and the electrodes are through with the oxygen flame treatment, a small portion of the composition, say a drop about the size of the head of a match, is placed inside the electrode and at the bottom thereof. The electrode is then again heated in the oxygen flame to cause the coating to fuse or melt so as to flow around throughout the entire insideof the cylin-= der and give it an even coating. The electrode is then cooled, and this process is repeated care. being taken'not to get any of the inside coating on the outside of the cylinder.

This coating upon analysis is found to con cording to the above method, the exterior coating is-applied. This exterior coating is made up of one part nickel oxide, one part sealing glass, and four parts powdered silica which material is ground to a very fine consistency and then held in suspension in a thin solution of alcohol. The mixture is applied to the outside of the cylinders by means of a small brush, and'the electrode is heated slowly in a flame so as to prevent the alcohol from evaporating too fast and causing the coating to chip 01f. This exterior coating serves to effectively prevent the electrical discharge from attacking the exterior of the electrode.

In preparing the interior coating, several barium compounds have been compared, but very poor or negative results have been obtained with all forms except that having the formula IBaOHaO. This barium compound appears to work very well and to have no bad effects whatever upon the color of the tube. Also, the ex terior coating has been found to be remarkably tree i'rom impurities that would'be released after the tube is placed in service so as to discolor it.

Having thus described my invention, what I I claim as new and desire to secure by Letters Patent is:

l. The process of making an electrode for gaseous conduction devices which consists of coating the interior of a cup-shaped body with a solution including carbon and BaOHzO thereafter heating said body and interior to partially convert the coating into barium carbide and thereafter coating the exterior of the body with a glass containing solution and heating the body to dry the coating and cause it to permanently adhere to the body.

2. The method of making an electrode for gaseous conduction devices of the cold electrode positive column type which consists in forming a base metal into cup shape and applying diiierent solutions to the interior and exterior thereof to provide coatings therefor, and heating each coating solution to convert the constituents thereof into a hard resistance coating.

3. The method of coating .an electrode for gaseous conduction devices which consists in forming a coating compound of barium oxide and carbon with the percentage of carbon by weight being less than 16% of barium applying said coating to the electrode and heating the electrode suiiiciently to convert at least a portion of the coating to barium carbide.

4. The method of coating an electrode 01'. cup shape for gaseous conduction tubes which consists in applying to the interior a compound containing carbon and barium oxide in proportionsof about one part carbon to twenty parts barium oxide by weight, applying to the exterior a coating compound made up principally of silica and heating the electrode to fuse the compounds thereon.

RICHARD E. MIESSE. 

